Use of a turbulence promoter in an electrochemical filter-press reactor: Consolidated evidence of significant enhancement of organics mass transport and degradation rates

Abstract

• Turbulence promotion enables a remarkable enhancement of the electrolysis performance. • The mass transfer coefficient is thus increased by approximately threefold. • The electrolysis time to attain 98% removal of bisphenol S is reduced by about 62%. • The organic load removal (mineralization) rate is almost doubled. • Significant energy savings are achieved for organics degradation by anodic oxidation. In this communication, consolidated evidence of the significant effect of turbulence promotion on organics anodic oxidation is presented. Thus, the performance of a filter-press reactor fitted or not with a turbulence promoter (three randomly superposed plastic meshes) is assessed using a recirculating flow system. For a given volumetric flow rate ( q V ), the mass transfer coefficient ( k m ) for the oxidation of the [Fe(CN) 6 ] 4− species at the surface of the boron-doped diamond anode (geometric area = 24.2 cm 2 ) is increased approximately threefold (e.g. to 9.44 × 10 −5 m s −1 at q V = 7.0 L min −1 ), indicating that mass transport is significantly enhanced by the presence of the turbulence promoter in the filter-press reactor. In fact, a given value of k m can be attained using a q V value that is only about one fifth that needed in the absence of the turbulence promoter. Using bisphenol S (BPS) as a model organic compound, an approximately threefold increase in its degradation rate is also brought on by the use of the turbulence promoter, which e.g. means a reduction of ~ 62% in the electrolysis time to attain 98% BPS removal. Additionally, the mineralization rate is doubled, which e.g. means a reduction of ~ 45% in the electrolysis time needed to remove 84% of the solution organic load. These results confirm that turbulence promoters in filter-press reactors indeed enable significant savings in the energy expenses associated to the electrochemical degradation of organics, greatly increasing the efficiency of the process.